1. Field of the Invention:
This invention relates to an apparatus for altering the pitch in the arrangement of wafers, and more particularly to an apparatus for altering the pitch in the arrangement of wafers which fits the operation of an automatic wafer transferring machine design for enabling wafers kept at a fixed pitch within one carrier to be transferred into another carrier and kept at a pitch which is a desired multiple of the first pitch.
2. Description of the Prior Art:
It is universally known that, in the process for the production of semiconductors, semiconductor wafers undergo various heat treatments, chemical treatments, and washing treatments. In the performance of these treatments upon the wafers, it has been customary for these wafers to be collectively handled in bunches as contained severally in carriers with a view to improving the efficiency of the treatments.
The carriers mentioned above are boxes which have grooves formed therein as spaced with a fixed pitch for keeping wafers neatly arranged therein. Of course, the efficiency of the treatments improves in proportion as the number of wafers contained in these carriers increases.
Depending on the nature of a treatment to be performed--depending on the choice between a heat treatment and an etching treatment, for example, --it becomes necessary to alter the pitch separating the individual wafers kept in the aforementioned carriers in order to derive a normal expected effect from the treatment.
The heat treatment, for example, is performed on the wafers separated with a very small pitch to ensure high efficiency of the treatment. In contrast, the CVD (chemical vapor deposition) treatment or the etching treatment is performed on the wafers separated widely as compared with the heat treatment, for the purpose of precluding possible unevenness of the effect of treatment.
Further depending on the difference in the nature of treatment mentioned above, the material of the carriers must be changed. For example, the heat treatment is performed on the wafers as contained in carriers made of quartz or the like, while the etching treatment is performed on the same wafers as contained in resinous carriers made of fluorocarbon polymers (Teflon) or the like.
When these wafers are transferred from one treatment to a subsequent treatment, therefore, it is necessary to perform an operation of causing the wafers disposed in the grooves separated with a certain pitch within a carrier made of a certain substance to be transferred into another carrier made of a different substance and set in place in the grooves separated with a different pitch.
Heretofore, this operation has been performed one by one either by a machine adapted to handle the wafers or directly by human hands with the aid of vacuum pincers.
Where the wafers are separated by one fixed pitch throughout all the treatments and their carriers are made of materials different from one treatment to another, it has been customary for the wafers to be transferred from a first carrier to a second carrier by first posing the first carrier so that the wafers are held therein in the horizontal direction, placing the second carrier in intimate contact with the first carrier in such a manner that their faces for entry of wafers will confront each other, and turning the joined carriers thereby causing the second carrier to underlie the first carrier and enabling the wafers to fall from the first carrier into the second carriers. Again in this case, the operation of transfer is effected by these carriers being handled in human hands.
The conventional practice, however, has entailed a disadvantage that during the transfer of the wafers from the first to the second carriers, the wafers are soiled or they are scratched or even broken owing to collision with the first and second carriers or they are injured as when they fall onto hard objects such as the floor surface.
Particularly in the case of the operation of bringing the first and second carriers into intimate mutual contact of their faces for entry of wafers, the wafers are liable to sustain scratches and chippings and to be contaminated with pulverized dust.
Moreover, the conventional practice has entailed a disadvantage that since there are steps in which the wafers have to be transferred one by one and handled directly by human hands, the transfer consumes much time and the efficiency of the work is poor and, as the result, the cost of semiconductor production is high.